Sampling errors and non sampling errors?

Sampling Errors: differences between your sample and the actual population that come about as a result of the observations that happened to be selected for the sample; (in sampling a population, regardless of how hard you try, there will always be some deviation from your sample as compared to your population because your sample may be slightly different from your population)

Non Sampling Error: differences due to mistakes in the acquisition of data or because of the improper formation of a sample.

• Errors in data acquisition: i.e. recording the wrong answer, measurements from faulty equipment, mistakes in transferring info from primary sources, or misinterpretation of questions/responses, etc.
• Non response errors: when people in the sample don't respond = no data
• Selection bias: when sampling makes it highly unlikely that some people will be included in the sample (i.e. selecting only those who are in the phone book would eliminate the chances for someone who isn't in the phone book to be selected)